Transmission system



July 23, 1929. 'J. R. FRY 1,722,045

TRANSMISS ION SYSTEM Filed Aug. 9, 1927 WWI-38 \IO/POGRAM fQU/PME/V 79 (MENTOR: J4 008 H firy Patented July 23, 1929.

UNITED STATES 1,722,045 PATENT OFFICE.

JACOB R. ERY, OF. MONTCLAIR, NEW JERSEY, ASSIGNOR T0 BELL TELEPHONE LAB: ORATORIES, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TRANSMISSION SYSTEM.

Application filed August 9, 1927. Serial No. 211,676.

This invention relates to transmission systems for distributing programs over physical lines and particularly to switching arrangements for the selection of the pro rams.

The objects are simplicity of operation from the subscribers viewpoint, low first cost, reliable, positive and non-marginal operation, low current consumption, and no impairment of line transmission qualities.

According to the invention there is provided a locking relay arrangement at the central oflice which can be operated from the subscribers station by the momentary actuation of one of several simple keys to select a desired program.

The drawing illustrates a subscribers line equipped with a program receiving set and controlling keys and a central station having three program distributing equipments together with relays for associating said equipments with the subscribers line. The receiving set consists of a loud speaking receiver 2 and an amplifier 3. The subscriber controls the selection of the programs by three keys, 4, 5, and 6, one for each program. The line 1 extends to the central oflice and terminates in a repeating coil 8.

The selecting mechanism at the central oifice consists of two sets of relays, relays 11 and12 comprising one set and relays 23 and 32 the other set. The relay 12 is equipped with two armatures 19 and 20 which are held in their normal positions by the springs 21 and 22 respectively. The ends of these armatures engage cam shaped latches 14 and 17 respectively of armatures 13 and 16 of the relay 11. With both relays deenergized and with the armatures 19 and 20 in their normal position, asshown in the drawing, the ends of these armatures are free from the latches 14 and 17. When, however, the relay 12 is energized and the armatures 19 and 20 rotate, they pass over the cam surfaces and are held b, the latches 14 and 17 after the coil 12 is eenergized. .To release the armatures -19 and '20 it is necessary to energize the coil 11 to attract the armatures 13 and 16. The armatures 13 and 16 are held in their normal positions by the springs 15 and 18, respectively.

C The construction of the'pair of relays 23 and 32 is exactly the same; the armatures 30 and 31 being normall held by the springs 33 and 34and in their a ternate positions being locked by the latches 25 and 28 of the armatures 24 and 27 respectively. The armatures 24 and 27 are similarly held in their normal positions by springs 26 and 29.

By energizing the relay 32 and the relay 11, the armatures of the relay 32 are locked in their alternate positions, and the armatures of relay 12, if they have been previously locked, are now unlocked. On the other hand, if relays 23. and 12 are energized simultaneously the armatures 19 and 20 are locked in their alternate positions while armatures 30 and 31 are released provided they have been previously locked in their alternate positions. If all four relays, 11, 12, 23 and 32, are operated simultaneously, and released, all armatures are restored to their normal posi-- tions. I

' Assume that the subscriber wishes to listen to the program being sent out from the'equipment 35. To do this he operates the nonlocklng key 6 for a brief interval. The key 6 drsconnects the tip conductor 9 from the recelvlng set and applies ground potential thereto. This results in the closure of a cir 'cuit through the windings of relays 12 and 23 to battery. Relay 23 operates and unlocks the armatures 30 and 31 which may have been operated on a previousoccasion. attracts its armatures 19 and 20 against the tension of springs 21 and 22, respectively, and these armatures are locked by the latches 14 and 17. After the key 6 is released, the tip conductor is restored and the relays 12 and 23 become deenergized. Although the relay 12 is deenergied, its armatures remain in their operated position since they are now latched.

The subscriber may now close the control I key 7 WlllCh completes a transmission circuit from the program set 35 to the receiving amplifier 3. The transmission circuit may be traced from the right terminal of the transformer 38 through the upper front contact of Relay 12 relay 12, through the right windings of repeatlng coil 8, lower front contact of relay 12,

to the other terminal of the transformer. The left windings of the repeating coil 8 are extended over the tip and ring conductors 9 and 10, through contacts of the keys 6, 5, 4,

and 7 tothe amplifier 3.

- This results in the closure of acircuit through tact of relay 32, upper back contact of relay 12, through the right windings of the-repeating ,coil 8, lower back contact ofrelay 12, lower front contact of relay 32 to the other side of the transformer 39.

If the subscriber wishes to listen to the third program the momentary operation of non-locking key 4 opens the circuit to the receiving set and places a ground potential on'both the tip and ring conductors of the line 1. This results in the momentary energization of all four relays 11, 12, 23' and 32. The relays 11 and 23 attract their armatures to allow the release of any armatures that may be latched at the time. When the energizing circuits are again opened, all four relays release leaving the armatures 19, 20, 30, and 31 in theirnormal positions. To insure that these armatures have time to release under this condition, the releasing operation of relays 11 and 23 may be made somewhat slower than that of relays 12 and 32. With all armatures in their normal positions, the transmission circuit may be traced from one winding of the transformer 40 through the upper back contacts of relays 32-and 12 to the right windings of coil 8 thence through the lower back contact of relays ,12 and 32 to the other terminal of the transformer 40. The

- program from the equipment 37 is transmitted over this circuit.

The receiver 2 and amplifier 3 at the subscribers station may be of any suitable types.

It will be seen from the foregoing descriptionthat the switching system disclosed provides a simple means for enabling a subscriber to select one of a few programs. By having the relays 11. 12, 23 and 32 symmetrically connected to the two sides of the line, the transmission qualities are not impaired, and by using theno'vel latching arrangement between the armatures the necessity of marginal operation is avoided which simplifies the subscribers equipment. Another 'obvious accomplishment of this arrangement is the low current consumption of the selecting mechanism since current is required only during the short intervals when the selecting keys are depressed.

What is claimed is: 1. In combination, a central office, a sub- I scribers line extending thereto, trunks at the central oflice, a pair of relays, each having a winding and an armature, means at the subated position during the period said circuits are open, and switching contacts actuated by said latter armature for selectively connecting the subscribers line to one of said trunks.

2. In combination, a central office, a subscribers line extending thereto, trunks at the central ofiice, a relay having a winding and armatures, a key at the substation for closing a circuit over one side of the line through the winding of said relay to operate its armatures, a second relay having armatures arranged to lockand hold in operated position the armatures of said first relay during-the period said circuit is open, contacts on the armatures of said first relay for connecting the subscribers line to one of said trunks, and a key at the substation for closing a circuit over the other side of the line to energize said second relay to unlock said armatures.

3. In combination, a central office, a subscribers line extendin thereto, trunks at the actuated position, keys at the substation, a

circuit rendered effective by'the operation of one of said keys for causing said locking means to lock the armatures of one relay and unlock the armatures of the other relay,

and contacts closed bythe armatures of said relays for selectively connecting the subscribers line to one of said trunks.

4. In combination, a central office, a subscribers line extending thereto, trunks at the central ofiice, a pair of relays, locking means for holding the armatures of said relays in actuated position, a pair of keys at the substation, means rendered effective by closure of one key for causin said locking means to lock the armatures o the first relay and unlock those of the second relay, means eifective by the closure of the other key for causing the locking means to lock the armatures of the second relay and unlock those'of the first relay, and contacts controlled by said armatures for selectively extending the subscribers line to one of said trunks.

5. In combination, a central ofiice having a plurality :of program equipments, a subscribers line leading to said ofiice, two airs of relays, one relay of each pair having ocking armatures, locking I mechanism controlled by the other relay of each pair, nonlocking keys at the substation for energiz- 1 6. In combination, a central oflice having a plurality of program distributing equipments, a subscriber s line leading to said office, a program receivin set at the substation,

i a relay, a key at thesu station for closing a momentary energizing circuit causing the relay to attract its armatures, locking means for holding said armatures in attracted position independentl of the energized condition of the relay, an contacts controlled by said ar- 1 matures for selectively extending the subscribers line to one of said equipments.

In witness whereof, I hereunto subscribe my name this 1 day of August A. D. 1927.

JACOB R. FRY. 

